Mr. Elmore's process, which is principally used for the making
of pipes. An iron mandrel is placed in insulated bearings in
a solution of copper sulphate, and a number of unrefined copper
bars placed round it some distance off. The mandrel is con-
nected to the negative pole, and the bars to the positive pole
of a dynamo, and the copper is thus decomposed and deposited
on the mandrel at a rate of about "2 inch in 170 hours. At the
same time a piece of polished agate presses on the mandrel, and
travels, slowly from end to end backward and forward, so as to
cover the whole surface as the mandrel slowly revolves; the
copper is therefore being burnished as fast as it is deposited,
and is thereby made very dense and strong. When the pipe is
sufficiently thick, the mandrel is taken off and steamed, which
allows the pipe to expand so as to be easily removed. It is
stated that copper pipes thus made are 50% stronger than those
that are either brazed or solid-drawn, and have a superior
ductility; while further strength can be imparted by rolling.
Manganese Steel is obtained by adding ferro-manganese
to iron or low-carbon steel. The first attempt, with 2^ % Mn, at
Terre Noire about 1885, resulting in a brittle metal, the
experiments were abandoned; but later, Mr. Hadfield (1887),
by pushing the percentage higher, obtained complete success.
The results at various degrees are very curious, and are probably
explained by the presence of carbon, which is inevitable.
CAST MANGANESE STEEL.
i\ : Produces no change if C be low.
3^ to 5 : Remarkably brittle cold, even with only '5% C, but not
so when hot.
5j to 6J : About the same.
6 \ to 7 : Strength and ductility increased ; magnetic quality
If not very tough, can be improved by water quenching.
Too hard for filing. " Strength equals crucible steel.
Entirely lacking in strength, no matter what the
9 to 10